Compressor unit for refrigeration installations

ABSTRACT

Compressor unit for refrigeration installations, comprising an electric motor having a shaft and a cooling fan outside the casing of the electric motor. The fan is fixed on an extremity of the shaft projecting outside said casing. Cam means are provided on the other extremity of the shaft, opposite to the fan. A hollow body surrounds the cam means. A cylinder formation is provided in the hollow body and extends perpendicular to the shaft in alignment with the cam means. A piston is slidable within the cylinder formation. The piston has a piston rod portion engaging the cam means. Inlet and outlet valve means are provided in the cylinder formation, duct and manifold means are provided for connecting the cylinder formation with the refrigeration circuit and sealing means for said cylinder formation and said piston.

Turci 1111 3,771,911 1451 Nov. 13, 1973 COMPRESSOR UNIT FOR REFRIGERATION INSTALLATIONS [75] Inventor: Bruno Turci, Ravenna, Italy [73] Assignee: IndelS.p.A.,SantAgataFeltria,

Italy 221 Filed: Jan. 10,1972

211 App]. No.: 216,373

Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard Sher Att0rneyGuido Modiano et al.

[5 7] ABSTRACT Compressor unit for refrigeration installations, comprising an electric motor having a shaft and a cooling fan outside the casing of the electric motor. The fan is fixed on an extremity of the shaft projecting outside said casing. Cam means are provided on the other extremity of the shaft, opposite to the fan. A hollow body surrounds the cam means. A cylinder formation is provided in the hollow body and extends perpendicular to the shaft in alignment with the cam means. A piston is slidable within the cylinder formation. The piston has a piston rod portion engaging the cam means. Inlet and outlet valve means are provided in the cylinder formation, duct and manifold means are provided for connecting the cylinder formation with the refrigeration circuit and sealing means for said cylinder formation and said piston.

1 Claim, 1 Drawing Figure COMPRESSOR UNIT FOR REFRIGERATION INSTALLATIONS BACKGROUND OF THE INVENTION The present invention relates to a compressor unit for refrigeration installations, comprising a compressor driven by an electric motor whose shaft carries a cooling fan at one extremity. Said compressor unit is adapted for low power refrigeration installations such as those installed in boats, caravans and the like.

Refrigeration installations of the aforementioned types suffer limitations because of restrictions or irregularity of the available space and the poor availability of energy. A further limitation is their sensitivity to variations in posture, i.e., the position of the vehicle on which said installations are mounted.

The main object of the present invention is to provide a compressor unit for medium and low power refrigeration installations particularly designed for use in mobile means such as watercraft, caravans and motor vehicles, which obviates the disadvantages arising with the compressor units intended for this use, i.e., a unit of high efficiency and able to operate in any posture.

The aforementioned object is attained by a compressor unit for refrigeration installations, comprising an electric motor having a shaft and a cooling fan outside the casing of the electric motor and fixed on an extremity of said shaft projecting outside said casing, cam means on the other extremity of said shaft, opposite to said fan, a composite hollow body surrounding said cam means, at least one cylinder formation in said h ollow body and extending perpendicular to said shaft in alignment with said cam means, a piston slidable within said cylinder formation and having a piston rod portion engaging said cam means, said cylinder formation having an arcuated ceiling and said piston having a cambered crown surface facing said arcuated ceiling, inlet and outlet valve means in said cylinder formation, duct and manifold means for connecting said clyinder formation with the refrigeration circuit, and sealing means for said cylinder formation and said piston.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF PREFERRED EMBODIMENTS The FIGURE shows the actual compressor 1 in its entirety, and the electric motor 2 which drives it.

The electric motor 2 comprises a casing 3 in which the stator 4 is disposed and which is closed by a back cap 6 and a front cap 7. The cap 7 also forms the body of the actual compressor 1. r

The back cap 6 comprises a series of radial fins 8 starting from the back support 9 of the driving shaft 10. In the back support 9 there is a seat 11 in which a bearing 12 is inserted, keyed on to the back end of said shaft 10.

The driving shaft emerges from the cap 6 and on its external end it carries a fan 14 for circulation of air, the operation of which will'be described hereinafter.

On that part of the driving shaft internal'to the casing 3 there is a shoulderring 15 which is inserted between said bearing 11 and the commutator 16. This latter is keyed on to a section 17 of the shaft 10 in which incisions 18 are made.

A brush holder assembly 20 is fixed in the back cap 6 by means of screws 19, so that its position corresponds with that of the commutator 16.

On the middle part 21 of the shaft 10, in which parallel incisions 22 are made, the rotary pack 23 is disposed with its relative'windings 24 connected to corresponding segments of the commutator 16.

Immediately after the middle part 21, the shaft 10 comprises an annular enlargement on which the lip of an oil seal gasket 25 rests tightly, and a zone 26 in engagement with a bearing 27 retained by a resilient ring 28. The bearing 27 and oil seal gasket 25 are housed in a seat 29 in the front cap 7 which is fixed to the casing by a series of stay bolts 30 which also fix the back cap 6.

The driving shaft 10 terminates at the end relating to the front cap 7 with a pin 31 which is eccentric and on which is keyed a rolling bearing 32 retained by a resilient ring 33. The bearing 32 is positioned in a cavity 34 which constitutes the inside of the base of the compressor 1 and is bounded by a tubular body 35 which projects axially from the cap 7 and a cover 36 which is fixed to said tubular body 35 by screws 37, with a gasket 38 of the toroidal type between. Both the tubular body 35 and cover 36 are finned with fins 39 and 40 respectively.

The tubular body 35 comprises a cylinder 41 which defines a cylindrical cavity 42 with an axis orthogonal to that of the shaft 10. A part 43 concentric with the cylinder 41 and rigid with the tubular body 35 houses a seat 44.

The seat 44 houses a bush 45 of anti-friction material and the bore of said bush has its axis perpendicular to that of the motor 10 and is also concentric with the cylindrical cavity 42. V

In the bore of the bush 45, a peg 46 is guided, resting lowerly on the bearing 32 and comprising a plate 47. The plate 47 has a lining 48 whose periphery slides along the surface of the cylindrical cavity 42. Said lining 48 is preferably of plastics material to reduce the moving mass, and is fixed 'to said plate 47 by embedding a central shank 49 in a hole formed axially in the peg 46 and embedding a projection 50 of said lining 48 into a peripheral groove in the plate 47. Said component comprising the plate 47 with its coupled lining 48 is the pumping piston of the compressor, as will be evident hereinafter. I

The lining 48 has a crowned surface in the form of a spherical cap and on said surface radial incisions 51 are made terminating at the peripheral edge. Towards the end of said incisions there are holes 52'which connect the chamber .53 locatedabove the crowned part with the backward chamber 42, which is in free communication with the interior of the cavity 34 by way of a large aperture 54.

Above the cylinder 41 and concentric with the cavity 7 42 there is a seat 55 comprising two rebates 55a and 55b, the first of which lies in a plane tangential to the summit of the lining 48 of the piston when this latter is located at its low dead point.

The rebate 55a comprises-concentric grooves, with similar grooves formed on a valve support plate 56 which rests on the rebate 55b and closes the cylinder 41.

Between the rebate 55a and the plate 56 a membrane 58 is clamped, made of resilient material and on which the piston 46, 48 acts.

The plate 56 comprises a spherical cap depression 57 which, taking account of the thickness of the membrane 58, is complementary to the crown of the lining 48. The plate 56 also comprises valves 59 and 60 for suction and delivery respectively. The suction valve 59 consists of a mushroom valve whose stem comprises grooves 61 for passage of the fluid, and a conical extremity terminating with an enlargement which retains a conical helical spring 62 for returning the valve 59. The valve 60 comprises a blade which intercepts the passage 63 of the fluid, its rise being limited by a stop 64 in the shape of an S and clamped axial to the blade 60 by a screw 65.

The valves 59, 60 control the passage of the fluid between the spherical depression 57 and the manifolds 66 and 67, formed by the upper surface of the plate 56 and the cavities in a head 68 fixed to the cylinder 41 by means of bolts 69 which also clamp the plate 56.

Between the plate 56 and head 68 there are concentric gaskets 70 and 71 which separate the suction manifold 66 and delivery manifold 77, and between the head 68 and cylinder 41 there is a further gasket 72.

Holes pass into the delivery manifold 67 and suction manifold 66 into which pipes 73 and 74 are fixed which connect the compressor 1 respectively to the inlet of the condenser 78 and outlet of the evaporator, this latter not shown.

The fan impeller 14 is housed in a delivery casing 75 which is fixed to the electric motor 2 by support means not shown in the FIGURE. The form of the delivery casing 75 is such as to axially deliver the air thrust by the fan impeller 14 so that it laps the whole surface of the compressor unit.

The delivery casing 75 also comprises a volute 76 consisting of a type of channel whose outlet consists of a marked enlargement 77 in the delivery casing, which is disposed in such a manner as to direct a part of the outlet air flow against the head 57.

The delivery casing 75 also acts as a support for the condenser 78 for positioning this latter in the path of the suction flow of the fan 14. The pipe 73 from the delivery manifold 67 terminates at the inlet 79 of the condenser 78.

The compressor described operates in the following manner.

vWhen the motor 2 operates, the eccentricity of the pin 31 gives rise to rectilinear reciprocating motion of the piston 46-48 with a corresponding reciprocating flexion movement of the membrane 58 and hence passage of fluid from the outlet of the evaporator to the inlet of the condenser.

Although its operation is substantially classical, the compressor unit described gives some remarkable advantages. Because of the particular form of the piston 46-48 there is high volumetric efficiency due to the fact that dead spaces are reduced in effect to just the outlet passage 63 for the compressed fluid, as the membrane 58 thrust by the piston46-48 perfectly mates' with the depression 57 formed in the plate 56 and representing the compression chamber.

The high volumetric efficiency also results from the large surfaceof the suction valve 59 because of which it is able to open at very low suction levels and form large passages for very small-rises. The aforementioned characteristic, i.e., the presence of very small dead spaces, is of essential importance in compressor units having a rather small piston displacement, as in the case considered.

The described compressor unit can tolerate very large overloads, due for example to an intake of liquid, because of the complete support given to the membrane 58 by the lining 48.

Perfect lubrication can be obtained for all moving parts. In particular it is possible to maintain a fluid film between the membrane 58 and lining 48 because the lubricant introduced into the cavity 34 can penetrate into the chamber 53 through the passage 52. This oil film does not give rise to hammering and the fact that it is located between the lining 48 and membrane 58 does not reduce the extent of flexion variations of this latter, as the incisions 51 form an escape path for the lubricant.

It should be noted that the piston return is determined both by the resilient action of the membrane 58 and by the pressure of the fluid in the suction manifold 66, because of which it is not necessary positively to connect the peg 46 to the cam 31.

It is important to note that in the compressor described there is prefect separation between the fluid re frigerant circuit and the lubrication circuit due to the membrane 58, because of which it is possible to orientate the compressor in any position without compromising its operation.

In one modification of the invention two opposing pistons are provided, driven by the same cam 31 in such a manner that when one of them is in the compression phase the other is in the suction phase and vice versa.

I claim:

I. A compressor unit for refrigeration installations, comprising an electric motor having a shaft and a cooling fan outside the casing of the electric motor and fixed on an extremity of said shaft projecting outside said casing, cam means on the other extremity of said shaft, opposite to said fan, a composite hollow body surrounding said cam means, at least one cylinder formation in said hoolow body and extending perpendicular to said shaft in alignment with said cam means, a piston slidable within said cylinder formation and having a piston rod portion engaging said cam means, inlet and outlet valve means in the ceiling of said cylinder formation, a resilient membrane defining with said ceiling a space sealingly separated from the portion of said cylinder formation in which the piston slides, said ceiling and the crown of said piston facing said membrane having a concave and a convex spherical surface respectively with equal radius of curvature, the improvement comprising radial incisions on the convex surface of said piston which communicate with peripheral holes axially extending through said piston. 

1. A compressor unit for refrigeration installations, comprising an electric motor having a shaft and a cooling fan outside the casing of the electric motor and fixed on an extremity of said shaft projecting outside said casing, cam means on the other extremity of said shaft, opposite to said fan, a composite hollow body surrounding said cam means, at least one cylinder formation in said hoolow body and extending perpendicular to said shaft in alignment with said cam means, a piston slidable within said cylinder formation and having a piston rod portion engaging said cam means, inlet and outlet valve means in the ceiling of said cylinder formation, a resilient membrane defining with said ceiling a space sealingly separated from the portion of said cylinder formation in which the piston slides, said ceiling and the crown of said piston facing said membrane having a concave and a convex spherical surface respectively with equal radius of curvature, the improvement comprising radial incisions on the convex surface of said piston which communicate with peripheral holes axially extending through said piston. 